Fixes ToolCallAccuracy raises ZeroDivisionError when called without any arguments.

[sahusiddharth]

• Fixes: #1684

1. Check for both empty dictionaries:
   • If both refs and preds are empty, return 1.0 as you specified in your logic.
2. Check for empty refs:
   • If refs is empty but preds is not, return 0.0 since there's nothing to compare.

[shahules786]

That's a nice catch @sahusiddharth